H-Bridge Constant Current Pacing Circuit Protection
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Solution Overview
Problem
Conventional constant current pacing circuits face challenges in matching transistors for equal current balancing and accurately generating low current bias signals, and they often suffer damage from high voltage defibrillation pulses due to lack of effective protection.
Innovation Solution
The implementation of an H-bridge circuit with a constant current source and diodes for protection, which applies a constant current output and safeguards against high voltage pulses by preventing external current flow to the source, ensuring efficient and noise-immune pacing while protecting the apparatus from defibrillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant current circuit uses a current mirror transistor pair to deliver the output current, then the output current can be maintained constant, but it is difficult to match transistors to obtain equal current balancing in the circuit
Solution Approach 1:
The patent introduces an intermediary circuit configuration that mediates between the constant current source and the H-bridge circuit. This intermediary structure enables constant current delivery while simplifying transistor matching requirements through its specific topological arrangement, resolving the contradiction between reliable constant current output and ease of manufacturing.
2Ease of operation
If conventional constant current pacing circuits are used, then pacing function can be provided, but damage can still be caused by a defibrillation pulse directly applied to a patient in parallel with the device
Solution Approach 1:
The patent implements preliminary protective measures by configuring the H-bridge circuit and constant current source in a manner that preemptively counteracts the harmful effects of defibrillation pulses. The circuit topology and component arrangement create inherent protection against voltage spikes and current surges from defibrillation, preventing damage before it occurs while maintaining full pacing functionality.
3Device complexity
If a constant current source is connected to the H-bridge circuit without protection, then the circuit can be simplified, but high voltage pulses can be applied to the patient via one or more other medical devices
Solution Approach 1:
The H-bridge circuit serves as an intermediary structure that mediates between the constant current source and the patient connection points. This intermediary configuration provides inherent protection against high voltage pulses from external medical devices while maintaining circuit simplicity, as the H-bridge topology naturally blocks reverse voltage and current flow paths that could cause damage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides accurate and efficient constant current pacing with enhanced protection from high voltage pulses, improving the reliability and safety of pacing therapies by maintaining a fixed output current and reducing noise interference.
Implementation Method 1
A diode is connected between the constant current source and the H-bridge circuit to prevent external current flow from the H-bridge circuit to the constant current source
Implementation Method 2
The diodes associated with the current switching elements (e.g., body diodes associated with field effect transistors) of the H-bridge circuit and the diode connected between the constant current source and the H-bridge circuit protect the constant current pacing apparatus from high voltage pulses applied to the patient via one or more other medical devices
Data Source
AI summary
A constant current pacing apparatus and method for pacing uses, for example, H-bridge circuitry and a constant current source connected to the H-bridge circuitry. Further, for example, protection is provided from high voltage pulses applied to the patient via one or more other medical devices.